Creating the QueryTrackerClient Application

To create the QueryTrackerClient application, you need to create the Executive Login and the Query Tracker Client windows , as well as the InitializeQueryProvider module.

Creating the Executive Login Window

The ExecutiveLogin class defines the Executive Login window.

Listing 4-10 shows the code for the frmExecutiveLogin.vb file that defines the ExecutiveLogin class:

Listing 4-10: The frmExecutiveLogin.vb File

 Imports System.Data.SqlClient Imports System.IO Imports System.Collections Imports System.Runtime.Remoting.Channels Public Class ExecutiveLogin    Inherits System.Windows.Forms.Form    Private Sub cmdGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdGo.Click       'Calling the Login function       executiveId = objQueryProvider.login(txtUserName.Text, txtPassWord.Text)       'Checking whether the login is succesful       If executiveId <> 0 Then          boolLoginConfirmaion = True          strUserName = txtUserName.Text          Dim objQueryTrackerClient As New QueryTrackerClient          objQueryTrackerClient.ShowDialog()       End If       Me.Close()    End Sub End Class 

 

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Figure 4-9 shows the output of Listing 4-10:

Figure 4-9: The Executive Login Window in Design View

Creating the Query Tracker Client Window

The QueryTrackerClient class defines the Query Tracker Client window.

Listing 4-11 shows the code for the frmQueryTrackerClient.vb file that defines the QueryTrackerClient class:

Listing 4-11: The frmQueryTrackerClient.vb File

 'This class provides methods to allow the executives to view the queries meant  'for them and mark them as attended when they have attended the query Public Class QueryTrackerClient Inherits System.Windows.Forms.Form    'Dataset variable to receive the dataset from queryprovider getQuery method    Dim ds As DataSet    'Dataset variable to return the dataset containing the queries that     'has to be marked as attended in the QueryTracker database    Dim updateds As New DataSet    'A datatable to store the QueryId of the queries that has been marked as attended by the executive    Dim queryTable As New DataTable("Queries")    Private Sub QueryTrackerClient_Closing(ByVal sender As Object, ByVal e As _    System.ComponentModel.CancelEventArgs) Handles MyBase.Closing       If queryTable.Rows.Count = 0 Then          Exit Sub       End If       'Assigning the queryTable datatable to updateds dataset       updateds.Tables.Add(queryTable)       objQueryProvider.updateQuery(updateds)    End Sub    Private Sub cmdAttended_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _    Handles cmdAttended.Click       'Check whether a query has been selected from the list view ListViewQuery       If ListViewQuery.SelectedItems.Count = 0 Then          MsgBox("Please select a query first", MsgBoxStyle.OKOnly, "WAIT HERE")          ListViewQuery.Focus()          Exit Sub       End If       'Marking the selected query as attended       ListViewQuery.SelectedItems.Item(0).SubItems(6).Text = "A"       Try          If queryTable.Rows.Count = 0 Then             'Creating the queryTable DataTable to contain the QueryId of the              'queries to be marked as attended             Dim queryDataColumn As New DataColumn             queryDataColumn.DataType = System.Type.GetType("System.Int32")             queryDataColumn.ColumnName = "QueryId"             queryTable.Columns.Add(queryDataColumn)             Dim querydataRow As DataRow = queryTable.NewRow             querydataRow.Item(0) = ListViewQuery.SelectedItems.Item(0).Text             queryTable.Rows.Add(querydataRow)             Else             'Adding new row to queryTable DataTable             Dim querydataRow As DataRow = queryTable.NewRow             querydataRow.Item(0) = ListViewQuery.SelectedItems.Item(0).Text             queryTable.Rows.Add(querydataRow)          End If          Catch ex As Exception       End Try    End Sub        Private Sub QueryTrackerClient_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load       If boolLoginConfirmaion = True Then          'Splashing a welcome message to the executive          lblWelcome.Text = "Welcome " & InitializeQueryProvider.strUserName          'Retrieving the queries for the executive          ds = objQueryProvider.getQuery(executiveId)          Try             If ds.Tables(0).Rows.Count = 0 Then                lblWelcome.Text = lblWelcome.Text & " : " & "No Queries For You."                ElseIf ds.Tables(0).Rows.Count = 1 Then                lblWelcome.Text = lblWelcome.Text & " : " & _                ds.Tables(0).Rows.Count & " Query For You."                Else                lblWelcome.Text = lblWelcome.Text & " : " & _                ds.Tables(0).Rows.Count & " Queries For You."             End If             'Enabling the cmdAttended command button             cmdAttended.Enabled = True             Dim rowcount As Integer             Dim tempListViewItem As ListViewItem             'Populating ListViewQuery with Query information retrieved by the dataset             For rowcount = 0 To ds.Tables(0).Rows.Count - 1                tempListViewItem = ListViewQuery.Items.Add(ds.Tables(0).Rows(rowcount).Item(0))                tempListViewItem.SubItems.Add(rowcount + 1)                tempListViewItem.SubItems.Add(ds.Tables(0).Rows(rowcount).Item(1))                tempListViewItem.SubItems.Add(ds.Tables(0).Rows(rowcount).Item(2))                tempListViewItem.SubItems.Add(ds.Tables(0).Rows(rowcount).Item(4))                tempListViewItem.SubItems.Add(ds.Tables(0).Rows(rowcount).Item(3))                'marking the query as unattended                tempListViewItem.SubItems.Add("U")             Next             Catch ex As Exception             MsgBox("Unable to retrieve queries", MsgBoxStyle.OKOnly, "Retrieval Error")          End Try          Else          Me.Close()       End If    End Sub        Private Sub cmdClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClose.Click       Me.Close()    End Sub End Class 

 

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The above listing defines the following methods:

• QueryTrackerClient_Load() : Retrieves and loads the queries specified for the executive in the ListViewQuery list view control.

• cmdAttended_Click() : Executes when an executive selects a query from the list and clicks on the Mark as Attended button to mark that query as attended to. This method updates the query status in the list as ˜A .

• QueryTrackerClient_Closing() : Executes when an executive closes the Query Tracker Client window. This method makes a request to the remoting object to update all the queries marked as attended.

Figure 4-10 shows the output of Listing 4-11:

Figure 4-10: The Query Tracker Client Window

Creating the InitializeQueryProvider Module

The InitializeQueryProvider.vb file defines the InitializeQueryProvider module.

Listing 4-12 shows the code for the InitializeQueryProvider.vb file:

Listing 4-12: The InitializeQueryProvider.vb File

 Imports System.Runtime.Remoting.Channels Imports System.Runtime.Remoting.Channels.Tcp Module InitializeQueryProvider    'A boolean variable to store the login status of the executive    Public boolLoginConfirmaion As Boolean    'A string variable to store the user name of the executive    Public strUserName As String    'A channelservices variable to register the tcp channel    Public cs As ChannelServices    'A tcpchannel variable to create an instance of tcpchannel    Public tcpchannel As New tcpchannel    'An instance of queryprovider remoting object    Public objQueryProvider As New QueryTrackerRemotingObject.QueryProvider    'A variable to hold the executive id returned by the login function provided by QueryProvider    Public executiveId As Integer    Sub main()       Try          'creating and registering tcp channel and as this is client you do not need to specify the port          tcpchannel = New tcpchannel          'registering the channel          cs.RegisterChannel(tcpchannel)          'create an instance of the remote object          objQueryProvider = Activator.GetObject(objQueryProvider.GetType, _          "tcp://192.168.0.12:8080/QueryProvider")          'Opening the frmExecutiveLogin form          Dim objExecutiveLogin As New ExecutiveLogin          objExecutiveLogin.ShowDialog()          Catch ex As Exception          MsgBox("Unable to locate the server", MsgBoxStyle.OKOnly, "Server not found")       End Try    End Sub End Module 

 

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In the above listing, the main() function creates a TCP channel as well as an instance of the remoting object, and invokes the Executive Login window.